JP2012193221A - Adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive sheet in which a peeling force does not become large even if a peeling rate becomes fast by using a mold release film with less influence of the peeling rate and accordingly, defects such as deformation of a substrate, and tunneling do not occur.SOLUTION: The adhesive sheet has ultraviolet curable adhesive layer on the mold release layer of a polyester film which has on one surface, a mold release layer comprising a thermosetting silicone having the silicon-hydrogen bond (SiH) of 20 mmol/mor less.

Description

  The present invention relates to a pressure-sensitive adhesive sheet in which an ultraviolet curable pressure-sensitive adhesive layer has stable release characteristics even at a high speed.

  In recent years, a bonding method using an adhesive has been widely used. As a method for applying the adhesive layer, an adhesive layer is formed on the release layer of the release film, and after bonding to the base material, the release film is peeled off and a laminate of the base material and the adhesive layer is attached to another base material. A laminating method is used. Although it was common to apply and dry a pressure-sensitive adhesive dissolved in a solvent as a method for applying the pressure-sensitive adhesive layer, in recent years, a method of forming a pressure-sensitive adhesive layer by using an ultraviolet curing reaction without using a solvent has been widely used. It has been.

  Automation is progressing about the process of peeling a release film, and the peeling speed is increasing. When the peeling speed is increased, the peeling force is increased, and problems such as deformation of the substrate occur. Moreover, when a light release film is used, problems such as tunneling occur.

  As a characteristic required for the release film, it is required that the influence of the peeling rate is small without affecting the ultraviolet curing reaction.

JP 1995-278500 A JP 2000-109779 A JP 2010-85578 A JP 2010-265440 A

  The present invention is intended to solve such problems, and the problem to be solved is that by adopting a release film that is less affected by the peeling speed, the peeling force can be increased even if the peeling speed is increased. As a result, it is an object of the present invention to provide a pressure-sensitive adhesive sheet that does not cause problems such as deformation of the base material and does not cause problems such as tunneling.

  As a result of intensive studies in view of the above problems, the present inventor has found that a release film made of a polyester film having a specific silicone layer can stabilize the peeling characteristics, and has completed the present invention. .

That is, the gist of the present invention is that an ultraviolet curable pressure-sensitive adhesive layer is provided on a release layer of a polyester film having a release layer made of thermosetting silicone having a silicon-hydrogen bond (SiH) of 20 mmol / m ² or less on one side. It exists in the adhesive sheet characterized by this.

  According to the present invention, it is possible to increase the use range of an ultraviolet curing pressure-sensitive adhesive which is a useless type pressure-sensitive adhesive, and to reduce the environmental load, and to speed up the release process of the release film. Is expensive.

  The polyester film as the substrate and support of the release film in the present invention refers to a molten polyester sheet that is melt-extruded from an extrusion die, which is extruded by a so-called extrusion method, and is subjected to stretching and heat treatment as necessary. Film.

The polyester constituting the release film used in the present invention is obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Representative polyesters include polyethylene terephthalate (PET), polyethylene-2,6-naphthalenedicarboxylate (PEN), and the like.
The polyester used may be a homopolyester or a copolyester. In the case of a copolyester, it may be a copolymer containing 30 mol% or less of the third component.

  The dicarboxylic acid component of the copolymerized polyester is selected from isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and oxycarboxylic acid (for example, P-oxybenzoic acid). The glycol component includes one or more selected from ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like.

  The polyester used in the present invention has a weather resistance agent, a light resistance agent, an antistatic agent, a lubricant, a light-shielding agent, an antioxidant, a fluorescent whitening agent, a matting agent, and a heat stability, as long as the gist of the present invention is not impaired. You may mix | blend an agent and coloring agents, such as dye and a pigment.

Examples of the particles to be blended in the film include silicon oxide, alumina, calcium carbonate, kaolin, titanium oxide, and crosslinked polymer fine powder as described in JP-B-59-5216. These particles may be used alone or in combination of two or more components. The content of the film layer to which these particles are added is usually 1% by weight or less, preferably 0.01 to 1% by weight, and more preferably 0.02 to 0.6% by weight. When the content of the particles is small, sufficient roughness cannot be given to the film surface, and in the film production process, there is a tendency that the surface is easily scratched or the winding properties are inferior.
Further, when the content of the particles exceeds 1% by weight, the degree of roughening of the film surface becomes too large, and the transparency may be impaired.

  The average particle diameter of the particles contained in the polyester film is usually 0.02 to 5 μm, preferably 0.1 to 3 μm, and more preferably 0.2 to 1.8 μm. When the particle size is less than 0.02 μm, sufficient roughness cannot be given to the film surface, and the winding characteristics in the film production process tend to be inferior. When the particle diameter exceeds 5 μm, when used as a polarizing plate release film, it may become a bright spot and hinder the defect inspection.

  On the other hand, in order to improve the transparency of the film, when a laminated film of two or more layers is used, a method of blending particles only in the surface layer is also preferably employed. The surface layer in this case is at least one of the front and back layers, and of course, particles can be blended in both the front and back layers.

  In the present invention, the method of blending the particles with the polyester is not particularly limited, and a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or before the start of the polycondensation reaction after completion of the transesterification reaction. The condensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder Etc.

  In addition, after melt-polymerizing polyester, this may be chipped, and solid-state polymerization may be further performed as necessary under heating under reduced pressure or in an inert gas stream such as nitrogen. The intrinsic viscosity of the obtained polyester is preferably 0.40 dl / g or more, and preferably 0.40 to 0.90 dl / g.

The thickness of the release film of the present invention is not particularly limited as long as it can be formed as a film and can be processed as a release film, but is usually 25 to 125 μm, preferably 25 to 25 μm. The range is 75 μm. If the film thickness is less than 25 μm, the film is insufficiently prone to tend to cause trouble in the process of peeling the release film.
When the film thickness exceeds 125 μm, the manufacturing cost increases, which is against the demand for lower prices.

  Next, although the manufacturing method of the release film of this invention is demonstrated concretely, as long as the summary of this invention is satisfied, this invention is not specifically limited to the following illustrations.

  First, the preferable example of the manufacturing method of polyester used by this invention is demonstrated. Here, an example in which polyethylene terephthalate is used as the polyester is shown, but the production conditions differ depending on the polyester used. According to a conventional method, esterification from terephthalic acid and ethylene glycol, or transesterification of dimethyl terephthalate and ethylene glycol, the product is transferred to a polymerization tank, and the temperature is increased while reducing the pressure. The polymerization reaction is advanced by heating to 280 ° C. under vacuum to obtain a polyester.

  Next, for example, the polyester chip obtained as described above and dried by a known method is supplied to a melt-extrusion apparatus and heated to a temperature equal to or higher than the melting point of each polymer and melted. Next, the molten polymer is extruded from a die and rapidly cooled and solidified on a rotary cooling drum so that the temperature is equal to or lower than the glass transition temperature to obtain a substantially amorphous unoriented sheet. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum. In the present invention, an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. In the present invention, the sheet thus obtained is stretched biaxially to form a film.

  Specifically describing the stretching conditions, the unstretched sheet is preferably stretched 2 to 6 times at 70 to 145 ° C. in the longitudinal direction to form a longitudinal uniaxially stretched film, and then 2 to 90 to 160 ° C. in the lateral direction. It is preferable to perform ~ 6 times stretching and heat treatment at 150 to 240 ° C for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the maximum temperature zone of the heat treatment and / or the cooling zone at the heat treatment outlet is preferable. Further, it is possible to add re-longitudinal stretching and re-lateral stretching as necessary. Furthermore, it is also possible to perform simultaneous biaxial stretching of the unstretched sheet so that the area magnification is 10 to 40 times.

  If the polyester film used by this invention is a range which does not impair the effect of this invention, what is called in-line coating which processes a film surface during a extending | stretching process can also be given. Although it is not limited to the following, for example, after the first stage of stretching is completed, before the second stage of stretching, improvement of antistatic property, slipperiness, adhesion, etc., secondary workability improvement, weather resistance, etc. In order to improve the property and surface hardness, a coating treatment with an aqueous solution, an aqueous emulsion, an aqueous slurry, or the like can be performed. Various coatings may be performed by offline coating after film production. Such a coat may be either single-sided or double-sided. The coating material may be either water-based and / or solvent-based for off-line coating, but is preferably water-based or water-dispersed for in-line coating.

  Next, formation of the release layer will be described. That is, the release layer constituting the release film in the present invention may be provided on the polyester film in the film production process such as the above-described coating and stretching method (in-line coating). So-called off-line coating, which is applied by the above method, may be employed, and any method may be employed. The coating stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the first stage of stretching may be completed and the coating treatment may be performed before the second stage of stretching. it can. When a release layer is provided on a polyester film by a coating and stretching method, the film can be applied simultaneously with stretching, and the thickness of the release layer can be reduced according to the stretching ratio. Can be manufactured.

  Moreover, it is preferable that the release layer which comprises the release film in this invention contains a curable silicone resin in order to make mold release property favorable. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

  As the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used. Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, X manufactured by Shin-Etsu Chemical Co., Ltd. -62-1387, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B, X-62-7052, X-62-7028A / B, X-62-7619, X-62 -7213, GE Toshiba Silicones Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, SM3200, SM3030, Toray Da DKQ3-3061, DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, SRX357, SRX211, SD7220, LTC303E, LTC750A, LTC760A, SP7259, BY24-468C, SP7248S, BY24 manufactured by Corning Co., Ltd. -252, SP7268S, SP7265S, LTC1000M, LTC1050L, SYLOFF7900, SYLOFF7198, SYLOFF22A, and the like. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  In the present invention, the residual amount of silicon-hydrogen bonds (SiH) in the silicone layer after the curing reaction needs to be 20 mmol or less per square meter. When it exceeds 20 mmol%, the peeling force increases at the time of high-speed peeling, which is not preferable.

  In the present invention, conventionally known coating methods such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating and the like can be used as a method for providing a release layer on the polyester film. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

In the present invention, the curing conditions for forming the release layer on the polyester film are not particularly limited. For example, when the release layer is provided by a coating stretching method (inline coating), it is usually 170 to 280. The heat treatment may be performed at a temperature of 3 to 40 seconds, preferably 200 to 280 ° C. for 3 to 40 seconds. On the other hand, when providing a release layer by off-line coating, heat treatment is usually performed at 80 to 200 ° C. for 3 to 40 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds. Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed irrespective of the coating extending | stretching method (in-line coating) or offline coating. In addition, a conventionally well-known apparatus and an energy source can be used as an energy source for hardening by active energy ray irradiation. The coating amount of the release layer from the viewpoint of coating property, usually 0.01 to 0.5 g / ^{m 2,} preferably in the range of 0.05 to 0.2 g / ^{m 2.} When the coating amount is less than 0.01 g / m ² , the coating property is lacking in stability, and it may be difficult to obtain uniform peeling characteristics. On the other hand, in the case of thick coating exceeding 0.5 g / m ² , the coating film adhesion, curability and the like of the release layer itself may be lowered.

  In the present invention, when a release layer is provided on the coating layer, the film may be temporarily wound after the coating layer is provided, and the release layer may be provided again. After the coating layer is provided, the release layer is continuously provided. A mold layer may be provided on the coating layer, and any method may be adopted.

  Regarding the release film in the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided on the surface where the release layer is not provided, as long as the gist of the present invention is not impaired.

  Further, the polyester film constituting the release film may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The release force of the release film in the present invention is usually in the range of 10 to 100 mN / cm, preferably 10 to 30 mN / cm. If the peeling force is less than 10 mN / cm, the peeling force may become too light and may cause a problem of easy peeling even in a scene where it is not necessary to peel off. On the other hand, if it exceeds 100 mN / cm, the peeling force May become too heavy and the patch may be deformed when peeled, or the adhesive may adhere to the release film side.

  Furthermore, the release film used in the present invention preferably has a residual adhesion rate in the range of 70% or more in order to maintain the adhesive force to the adherend. If the residual adhesive rate is less than 70%, the film is too slippery, and thus problems such as slippage of the nip roll may occur in the production process, or the adhesive strength of the patch may be reduced.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measuring method used in the present invention is as follows.

(1) Measurement of release layer coating amount Mold release under the following measurement conditions by FP (Fundamental Parameter Method) using a fluorescent X-ray measurement apparatus (Shimadzu Corporation, model “XRF-1500”). The amount of silicon element on the surface provided with the release layer and the surface without the release layer was measured, and the difference was taken as the amount of silicon element in the release layer. Next, the coating amount (Si) (g / m ² ) as a unit of —SiO (CH ₃ ) ₂ was calculated using the obtained amount of silicon element.
"Measurement condition"
Spectral crystal: PET (pentaerythritol)
2θ: 108.88 °
Tube current: 95 mA
Tube voltage: 40 kv

(2) Evaluation of peel strength (F) of release film Affixed with one side of double-sided adhesive tape (Nitto Denko "No. 502") on the release layer surface of the sample film, then cut into a size of 50mm x 300mm After that, the peel strength after standing for 1 hour at room temperature is measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under the condition of a tensile speed of 300 mm / min.

(3) Evaluation of residual adhesive rate of release film << residual adhesive strength >>
Nitto Denko (manufactured) No. on the surface of the release layer of the sample film. The 31B adhesive tape is subjected to one reciprocating pressure bonding with a 2 kg rubber roller, and heat-treated at 100 ° C. for 1 hour. Next, the sample film was peeled off from the pressure-bonded sample. The adhesive strength of the 31B pressure-sensitive adhesive tape is measured according to the method of JIS-C-2107 (adhesive strength to stainless steel plate, 180 ° peeling method). This is the residual adhesive strength.
《Basic adhesive strength》
Using the same tape (No. 31B) as in the case of residual adhesive force, an adhesive tape is pressure-bonded to a stainless steel plate according to JIS-C-2107, and measurement is performed in the same manner. The value at this time is defined as the basic adhesive strength. Using these measured values, the residual adhesion rate is determined based on the following equation.
Residual adhesion rate (%) = (residual adhesive force / basic adhesive force) × 100
The measurement is performed at 23 ± 2 ° C. and 50 ± 5% RH.

(4) Evaluation of remaining SiH amount of release film Sample film 40 cm ² is cut into several square mm, put into a 20 mL headspace bottle, 3 mL of potassium hydroxide saturated butanol solution is added and sealed. Next, after heating for 2 hours at 50 ° C. using a dryer and cooling to room temperature, 1 mL of the gas phase in the bottle was injected into the GC with a gas tight syringe, and measurement was performed.
《Quantitative method》
1 mL of standard hydrogen gas (purity 99.9%) was collected with a gas tight syringe and injected into a vacuum bottle (1000 mL) to adjust 1 μL / mL (1000 nL / mL) of standard gas. A calibration curve was prepared by injecting 1 mL of standard hydrogen having a constant concentration diluted with air into the GC, and the amount of hydrogen per mL of sample gas was determined. The amount of hydrogen generated in the gas phase portion 17 mL obtained by subtracting the volume 3 mL of the potassium hydroxide saturated butanol solution added from the bottle volume 20 mL is calculated, the amount of hydrogen generated per area of the sample film is calculated, and the number of moles per square meter is calculated. Calculated.
"Measurement condition"
GC: 6890N made by Agilent Technologies
Column: Molsive 5APLOT (0.53mmφ × 25m, df = 50μm)
Column temperature: 40 ° C (3 min)
Column pressure: Constant flow mode (40 kPa)
Column flow rate: 5 mL / min (N ₂ )
Inlet temperature: 150 ° C
Injection volume: 1 mL
Detector: TCD
Detection temperature: 150 ° C

(5) Sheet Appearance In a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer coated with an ultraviolet curable pressure-sensitive adhesive was provided on the release surface of a release film and a support was bonded, the appearance was visually observed to evaluate the shape.
(Appearance is good) ○>△> × (Appearance is bad)

(6) Adhesive Peeling Force An adhesive sheet provided with an ultraviolet curable adhesive layer on the release surface of a release film and bonded to a support is cut into a size of 50 mm × 150 mm, and then a tensile tester (Co., Ltd.) Using Intesco “Intesco Model 2001”), peeling was performed 180 ° under a tensile speed of 300 mm / min, and the peeling force was measured.

(7) Adhesive high-speed peel force After the UV-cured pressure-sensitive adhesive layer is provided on the release surface of the release film and the support is bonded, the adhesive sheet is cut into a size of 50 mm × 200 mm, and then a high-speed peel tester (tester Sangyo Co., Ltd.) was used, and the peel strength was measured by peeling 180 ° under the condition of a tensile speed of 10 m / min.

<Manufacture of release film>
A polyethylene terephthalate film (Diafoil T100-75 manufactured by Mitsubishi Plastics, Inc.) is used as a base film, and a release agent having a release agent composition shown below is applied (after drying) to 0.06 to 0.1 g / m. ^The release film was obtained under the conditions of a Mayer bar coat method so as to be ² and a dryer temperature of 120 ° C. and a line speed of 30 m / min.

(Release film A)
Curing type silicone resin (DKQ3-33061: manufactured by Toray Dow Corning) 100 parts Curing agent (SRX67: manufactured by Toray Dow Corning) 0.5 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 500 parts

(Release film B)
Curing type silicone resin (DKQ3-33061: manufactured by Toray Dow Corning) 100 parts Curing agent (SRX67: manufactured by Toray Dow Corning) 0.5 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 750 parts

(Release film C)
Curing type silicone resin (LTC-303E: manufactured by Toray Dow Corning) 100 parts Curing agent (SRX212: manufactured by Toray Dow Corning) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

(Release film D)
Curing type silicone resin (LTC-303E: manufactured by Toray Dow Corning) 100 parts Curing agent (SRX212: manufactured by Toray Dow Corning) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 2300 parts

(Release film E)
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

(Release film F)
Curing type silicone resin (KS-778: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

(Release film G)
Curing type silicone resin (KS-774: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

(Manufacture of adhesive sheet)
UV release adhesive (SK Dyne syrup C 100 parts, curing agent 1 part, photoinitiator 3 parts: manufactured by Soken Chemical) on the release layer surface of release films A to G so that the thickness after the curing reaction is 50 μm And the curing reaction of the pressure-sensitive adhesive composition is completed using an ultraviolet irradiation device (high pressure mercury lamp, output 80 W / cm). The ultraviolet irradiation intensity was 1200 mJ / cm 2. A pressure-sensitive adhesive sheet was prepared by laminating a 25 μm-thick polyester film for a support material. The obtained results are summarized and shown in Tables 1 and 2 below.

  The pressure-sensitive adhesive sheet of the present invention can be suitably used in various bonding processes.

Claims (1)

A pressure-sensitive adhesive sheet comprising an ultraviolet-curing pressure-sensitive adhesive layer on a release layer of a polyester film having a release layer made of thermosetting silicone having a silicon-hydrogen bond (SiH) of 20 mmol / m ² or less on one side.